UR-98 is an XFree86 input driver for the Union Reality
UR-F98 headtracker.

The UR-98 driver functions as a pointer input device,
and can be used either as an additional input device or as the X server's
core pointer. The driver provides support for the three axes, throttle and
four buttons of the controller. If mapped as the core pointer the headtracker
provides headtracking to try and place the mouse cursor where you look.
As a secondary input device the unit can be used for gaming, for example
to provide the look up/down and the turn in quake, and with the Z axis
bound to ack/forward to provide movement control.

The default mapping maps
left-right movement to X, up-down movement to Y and near/far movement to
the Z axis. The throttle is mapped as the fourth axis by default but can
also be mapped as button 5.

For use in "head only" mode the Z axis can be
mapped as a button. This allows the user to select objects with head/neck
movement alone but takes some practice to use well.

The hardware or kernel driver has some idiosyncracies.
Notably on kernel initialization the interface occasionally gets into a
state where the readings rapidly cycle left-right-left-right or top-bottom-top-bottom.
In those cases it seems to be neccessary to unload the driver, unplug,
replug and reload the joystick drivers. Once it initializes sanely it remains
sane.

If the device refuses to work check the gray/black cables are plugged
into the right ports on the unit. Be careful about this as crossing the
cables can lead to the device failing with a nasty burning electronics
smell. The author writes from direct experience.